1. Field of the Invention
The present invention relates to the manufacture of laminated safety glass for automobile vehicles, and more particularly to an apparatus for the pressing of laminated glass/plastic composites of a highly curved shape, with side wings sharply bent in the direction of the concave side of the composite. The apparatus can be used in an automatically operated plant for the manufacture of laminated safety glass, and includes a device for the mechanical pressing of the glass/plastic composite and devices for moving the composite into and out of the press.
2. Description of the Prior Art
It is well known that laminated safety glass, particularly that used in windows of automobiles or other vehicles, comprises two curved sheets of glass with a layer of plastic interposed therebetween acting as an adhesive for the two sheets of glass.
In the following, the glass/plastic composite will be indicated by the term "sheet of glass".
In the manufacturing process of such a product, a step is provided for mechanically pressing together the sheets of glass and the plastic layer, in order to expel any air contained therebetween and to bond the edges. This prevents, in a successive autoclave treatment at a controlled temperature and pressure, any undesirable air penetration which could detach the glass and plastic layers from each other.
Apparatuses for carrying out this pressing step are well known in the prior art. Generally such apparatuses comprise a set of horizontally arranged pressing rolls, mounted in a cage arranged so as to be angularly shifted along a curved path.
In apparatuses of this type the sheet of glass enters horizontally between the rolls, and while these are pressing the glass, the mounting cage rotates horizontally about its own axis so as to lay the sheet of glass on a discharging conveyor.
It is necessary that the sheet of glass be fed to the pressing rolls at a properly set entry angle to prevent the sheet from being broken. To this end, manpower is provided to manually assist the sheet to enter at the proper angle, or else automatic centering devices are used.
In a cycle of manufacture of laminated safety glass, there are generally two pressing steps. The first step serves the purpose of expelling the air trapped between the layers, and the second step bonds the edges after subjecting the sheet of glass to light heating for softening the intermediate plastic layer.
The first of the two pressing steps is carried out in a horizontal position since the adherence between the glass and plastic layers is not yet sufficient.
In recent years, glass for automotive vehicles, particularly windscreens and rear windows, has become increasingly curved, and the wings, for aerodynamical and aesthetic reasons, are sharply bent in the direction of the concave surface of the glass window.
Consequently a horizontal pressing apparatus, such as previously described and known from the Italian Pat. No. 1142562, results in a high risk of breaking the glass, even when manpower is present. In fact, it can be easily understood that, when a sharply bent wing enters the pressing rolls, all the windscreen weight is discharged on the entry line, with the attendant risk of breaking the glass.
An automatic centering device does not avoid such a risk.